Lycopene, which provides most red-hued fruits, like tomatoes, pink grapefruit, and red peppers, their color. About 80% of the lycopene we ingest comes from tomato-based products, and over the last decade, studies have found that the lycopene in tomatoes could be linked to a reduced rate of prostate, lung, and stomach cancers.

Lutein, which is found in dark leafy greens like kale and Brussels sprouts and has also been shown to reduce the risk of eye diseases, like age-related macular degeneration.

A major nutritional boost

Flickr / jules
So just how much more of these disease-fighting carotenoids do you get by pan frying them in oil (not to be mistaken for deep frying, which is an entirely different method of cooking)?

We asked Guy Crosby, who has spent 30 years in the commercial food industry business and is now the editor for America's Test Kitchen and teaches a food science course at the Harvard School of Public Health. You can learn more about him on his site "The Cooking Science Guy."

As Crosby explains:

"In the fresh tomato most of these [carotenoid] pigments are all tied up with proteins," Crosby told Business Insider. "If you cook the tomato you break down the bonds between the proteins and the pigments — the lycopene — and you absorb about four times more lycopene into your blood from cooked tomatoes than from fresh tomatoes."

But wait, there's more: Carotenoids fall under a class of vitamins called fat soluble vitamins, as opposed to water soluble vitamins like Vitamin C and some types of Vitamin B. This means that carotenoids will dissolve in fats, for example the fat in frying oil, just like the Vitamin B-6 in broccoli dissolves in water when you boil it.

"Since lycopene is soluble in oil, if you cook your tomatoe in olive oil, you'll absorb two times more again above and beyond from what you absorb from cooking tomatoes without the oil," Crosby said.

Now, if you're watching your waist line, it's important to limit the amount of fat you ingest daily. And frying anything is certainly going to up the fat content.